Recently, in accordance with the rapid development of a cellular phone, a notebook, and an electric car industry, an international demand on a mobile energy source is gradually increased. As the above-mentioned energy source, particularly, utilization of a lithium secondary battery has explosively increased. Currently, a lithium secondary battery industry is developed in Korea, Japan, and China, and in accordance with a rapid increase in demand of the lithium secondary battery, consumption of lithium, which is a major substance, has been rapidly increased. Further, since lithium is used to increase tritium in a thermonuclear fusion power generation which is expected as a next generation energy source, a demand on lithium has gradually increased.
It is estimated that about 250 billion tons of lithium ions are dissolved in seawater, and as a result, the seawater has begun to be recognized as an important lithium supplying source. However, since concentration of lithium is very low at 0.17 mg per 1 liter of seawater, when considering economical efficiency for recovering lithium ions, a system cable of recovering lithium ions selectively and at low costs is required.
In order to recover lithium ions from seawater, methods such as an ion-exchange adsorption method, a solvent desorption method, and a coprecipitation method have been researched, and among these methods, a lithium ion recovering method using a manganese oxide-based inorganic adsorbent having ion-exchange characteristics having very high selectivity is one of most preferable methods. As a result, various manganese oxide-based inorganic adsorbent have been developed (see, Ind. Eng. Chem. Res., 40, 2054, 2001). The manganese oxide-based inorganic adsorbent adsorbs lithium ions in a liquid by ion-exchange of hydrogen ions and lithium ions in the liquid including the lithium ions, that is topotactic extraction, and consequently, the inorganic adsorbent in which the lithium ions are adsorbed enables the lithium ions to be recovered by the ion-exchange of the hydrogen ions and the lithium ions in a diluted hydrochloric acid aqueous solution. Thus, the above-mentioned manganese oxide-based inorganic adsorbent has an advantage in that it may be repeatedly used.
However, in a process according to the related art in which lithium manganese oxide powders, which are particles having a size of about 10 μm, of several tens kilograms (kg) or more, and further a great quantity of lithium manganese oxide powder of units of tons or more are processed by an acid aqueous solution to form manganese oxide, a large acid resistance water tank and a flowing apparatus for allowing the acid aqueous solution to be effectively reacted with the powder are required.
Further, a process of separating and drying the liquid obtained after the lithium manganese oxide powders are processed by the acid aqueous solution is additionally required. As such, the lithium ion recovering apparatus according to the related art and the lithium ion recovering method using the same are very complex and inconvenient, and have problems in that attention is required in a processing operation, and the like.
As the Related Art, Japanese Patent Laid-Open Publication No. 2002-088420 (Related Art 1 titled “Apparatus for Recovering Lithium from Seawater”) includes a ship body having a seawater variable means, a seawater introducing path communicating a bottom surface of a hold part of the ship body into the sea to provide a communicating path at a lower side of the ship body, nets installed on a side of a seawater inlet and a side of a seawater outlet of the hold part, a lithium adsorbent received between the nets in the hold part to have granularity greater than a mesh of the net, a seawater circulating means for pressing the seawater introduced from the outside of the ship body into the hold part to pass through the lithium adsorbent together with the seawater introduced from the seawater introducing path, and then circulating and draining the seawater passing through the lithium adsorbent outside of the hold part, a draining means for discharging the remaining seawater in the hold part, a desorption solution injecting and recovering means for injecting a desorption solution into the hold part and recovering the desorption solution in which lithium is dissolved from inside of the hold part, and a desorption and liquefaction circulating means for circulating the desorption solution in the hold part to desorb lithium from the lithium adsorbent 10.
However, according to Related Art 1, there is a problem in that a large amount of power is required to introduce the seawater into the ship body and discharge the seawater.
To solve the above-mentioned problem, the applicant has proposed a lithium recovery station in Related Art 2 (Korean Patent Publication No. 1383299) including: a floating body floating on the sea; a moving means installed on the floating body and for moving a lithium adsorbent; an adsorption tank formed in a structure in which upper and lower surfaces thereof are opened on the floating body and the lithium adsorbent passes through so that the lithium adsorbent vertically passes through the floating body; a cage formed in a frame structure to be connected to the lower surface of the adsorption tank, and in which the lithium adsorbents passing through the adsorption tank are sequentially stacked therein and lithium ions are adsorbed in a state in which the cage is immerged in the seawater; a cleaning tank installed on the floating body and for cleaning the lithium adsorbent in which the lithium ion lifted by the moving means from the cage is adsorbed; and a desorption tank installed on the floating body and for desorbing the lithium ion of the lithium adsorbent in which the lithium ion moved from the cleaning tank by the moving means is adsorbed.
However, the lithium recovery station according to Related Art 2 adsorbs lithium in a manner in which the lithium adsorbent is held in the adsorption tank and the cage which are installed on the station itself floating on the sea. When an amount of lithium adsorbent used in an enlargement process becomes large, large sized adsorption tank and cage are required to be manufactured to accommodate the large amount of lithium adsorbent. As a result, it causes a super-sized lithium recovery station.
Therefore, according to Related Art 2, there was a problem in that costs for constructing and maintaining a plant of the lithium recovery station at the sea are quite expensive.